JP2020009536A - White organic light-emitting device - Google Patents

Abstract

To achieve both of the ensuring of a desired color reproduction range and the suppression of a viewing angle dependence.SOLUTION: In a white organic light-emitting device, an organic layer 15 has a blue light-emitting layer 15c containing a light-emitting molecule which emits blue light, and a long-wavelength light-emitting layer 15b containing a light-emitting molecule which emits red light and a light-emitting molecule which emits green light. The long-wavelength light-emitting layer 15b is disposed between the blue light-emitting layer 15c and a reflective electrode 13. The blue light-emitting layer 15c is disposed in a location that satisfies the formula (1) below. The white organic light-emitting device has a resonator structure formed between the reflective electrode 13 and a light lead electrode 16, and it has a resonance maximum peak wavelength in a blue-color wavelength region. z=φ×λ/4π (1), where z is an optical distance between an interface of the blue light-emitting layer 15c on the side of the reflective electrode 13 and the reflective electrode 13, φ is a reflection phase of the reflective electrode 13 in an emission wavelength region of the blue light-emitting layer, and λis a wavelength of a visible light region.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a white organic light emitting device.

2. Description of the Related Art In recent years, an organic electronic element using an organic compound capable of performing a coating film formation and a low-temperature process on an electronic functional element using an inorganic compound has been studied. In particular, the organic light-emitting device is also called an organic electroluminescence device or an organic EL device, and is being rapidly developed.
For full color display devices, it is necessary to obtain basic colors of red (R), green (G), and blue (B). As a method of obtaining the basic colors of RGB, a method of separately applying each light emitting layer emitting red, green, and blue to each sub-pixel, or a method of performing color separation using an RGB color filter using a white light emitting element, and the like can be considered. In recent years, miniaturization of multiple pixels of a full-color display device has been advanced, and it has been difficult to miniaturize a high-definition mask and perform high-accuracy alignment by a method of separately applying three colors of RGB organic light-emitting layers, thereby causing a decrease in yield. . On the other hand, the method using a white light emitting element and an RGB color filter is effective in improving the yield because it is not necessary to separately apply a high-definition mask. On the other hand, it has been proposed to emit light at a light emitting position suitable for each light emitting color emitted from a light emitting layer as a high efficiency of a white light emitting element (Patent Document 1).

JP 2011-76769 A

  The device mode disclosed in Patent Document 1 for increasing the efficiency of the white light emitting device is effective in improving power consumption as a display. However, such devices as controlling the film thickness of each of the R, G, and B light emitting layers, controlling the dopant concentration of light emitting molecules, designing interference for reproducing a wide color gamut, and optimizing the charge recombination probability in each light emitting layer. The production becomes difficult, and the yield is reduced. Further, since a wide spectrum unique to organic materials is emitted, it is difficult to increase color purity, and it has been difficult to achieve both a desired color reproduction range as a display and suppression of viewing angle dependence.

The white organic light emitting device of the present invention,
A reflective organic electrode, an organic layer, and a light extraction electrode, a white organic light-emitting element having, in this order,
The organic layer has a blue light emitting layer containing a light emitting molecule that emits blue light, and a long wavelength light emitting layer containing a light emitting molecule that emits red light and a light emitting molecule that emits green light,
The long-wavelength light-emitting layer is disposed between the blue light-emitting layer and the reflective electrode,
The blue light emitting layer is disposed at a position satisfying the following formula (1):
It has a resonator structure formed between the reflection electrode and the light extraction electrode, and has a resonance maximum peak wavelength in a blue wavelength region.
z = φ × λ ₁ / 4π (1)
z: the optical distance between the interface of the blue light emitting layer on the reflective electrode side and the reflective electrode φ: the reflection phase λ _{1 of the} reflective electrode in the emission wavelength region of the blue light emitting layer: wavelength in the visible light region

  The white organic light emitting device of the present invention has a wide color reproduction range and excellent viewing angle dependency. Further, the yield can be improved by simplifying the fabrication of the device.

It is a cross section showing an example of a white organic light emitting element concerning the present invention. It is a figure showing the relation between resonance effect intensity and wavelength. It is a cross section showing an example of the display concerning this embodiment. FIG. 1 is a schematic diagram illustrating an example of a display device according to an embodiment. FIG. 1 is a schematic diagram illustrating an example of a display device according to an embodiment. FIG. 1 is a schematic diagram illustrating an example of an imaging device according to an embodiment. It is a schematic diagram showing an example of the portable device according to the present embodiment. It is a schematic diagram which shows an example of the lighting device which concerns on this embodiment. It is a figure showing the fluorescence spectrum of the luminescence molecule used by simulation. FIG. 4 is a diagram illustrating transmission characteristics of a color filter used in a simulation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The dimensions of each part of the drawing are different from the actual ones. In addition, well-known or known techniques in the art are applied to parts not specifically illustrated or described in this specification.

≪White organic light emitting device≫
The white organic light emitting device of the present invention will be described in detail. FIG. 1 is a schematic sectional view showing an example of the white organic light emitting device 100 of the present invention. The white organic light-emitting device 100 shown in FIG. 1 has a reflective electrode 13, an organic layer 15, and a light extraction electrode 16 on a substrate 10 in this order, and emits white light. The organic layer 15 has a blue light emitting layer 15c containing a light emitting molecule emitting blue light, and a long wavelength light emitting layer 15b containing a light emitting molecule emitting red light and a light emitting molecule emitting green light. The long wavelength light emitting layer 15b is disposed between the blue light emitting layer 15c and the reflective electrode 13. A transparent sealing layer 17 is provided on the light extraction electrode 16 to protect the organic light emitting element from external moisture and oxygen.

<Reflective electrode 13>
The reflective electrode 13 is preferably made of a metal material having a reflectance of 80% or more. Specifically, for example, an alloy obtained by adding Si, Cu, Ni, Nd, Ti, or the like to a metal such as Al or Ag can be used. The reflectance refers to the reflectance at the wavelength of light emitted from the light emitting layer. Further, the reflective electrode 13 may have a barrier layer on the surface on the light extraction side. As a material of the barrier layer, a metal of Ti, W, Mo, or Au or an alloy thereof is preferable, and a thickness of the barrier layer is preferably 1 nm or more and 10 nm or less.

<Organic layer 15>
The organic layer 15 may have a multilayer structure as shown in FIG. For example, when the reflective electrode 13 is an anode, the element shown in FIG. 1A has a white light emitting layer including a hole transport layer 15a, a long wavelength light emitting layer 15b, and a blue light emitting layer 15c, and an electron transport layer 15d. Can be. A hole injection layer, an electron block layer, a hole block layer, an electron injection layer, and the like can be appropriately provided in the organic layer 15. As the electron injection layer, a known material such as an inorganic substance such as LiF, CsF, Cs ₂ CO ₃ , and Li ₂ O and a lithium complex such as lithium quinolinol (Liq) can be used.

  For the electron transport layer 15d, a known electron transport material can be used. A phenanthroline derivative, a quinolinol complex, or the like can be used. It is preferable to use a wide gap material such as a polycyclic aromatic hydrocarbon or a heterocyclic aromatic as a hole blocking layer between the electron transport layer 15d and the blue light emitting layer 15c as appropriate.

  As the hole transport layer 15a, a known hole transport material can be used. A triarylamine derivative, a carbazole derivative, a thiophene derivative, or the like can be used. An electron blocking material can be appropriately inserted between the hole transport layer 15a and the long wavelength light emitting layer 15b. As the electron blocking material, one in which LUMO is shallower (smaller in absolute value) than the light-emitting layer is preferable, and a carbazole derivative and a triarylamine derivative are particularly preferable. Further, a material having a strong electron-withdrawing property such as molybdenum oxide or F4-TCNQ (tetracyanoquinodimethane) can be used as a hole injection layer between the reflective electrode 13 and the hole transport layer 15a.

  The hole transport layer 15a and the electron transport layer 15d may have a desired optical film thickness to satisfy the interference conditions described later. As the physical film thickness, preferably, the hole transport layer 15a has a thickness of 10 nm or more and 50 nm or less, and the electron transport layer 15d has a thickness of 100 nm or more and 150 nm or less. These values may vary depending on the number of layers to be stacked and the optical characteristics of each layer. .

  The light emitting layer has a long wavelength light emitting layer 15b and a blue light emitting layer 15c. As shown in FIG. 1B, a spacer 15e for appropriately adjusting the light emission balance of the light emitting layer may be introduced between the long wavelength light emitting layer 15b and the blue light emitting layer 15c. The long wavelength light emitting layer 15b contains at least a green light emitting molecule and a red light emitting molecule. The long wavelength light emitting layer 15b and the blue light emitting layer 15c can be formed by appropriately co-evaporating light emitting molecules of each color with a predetermined dopant concentration on a host material. The blue light emitting layer 15c preferably contains a blue dopant concentration of 0.1 wt% or more and 10 wt% or less with respect to the host material. In the long-wavelength light-emitting layer 15b, green light-emitting molecules are preferably contained at 0.5 wt% to 10 wt%, and red light-emitting molecules are preferably contained at 0.5 wt% to 5 wt% with respect to the host material. Can be formed. The thickness of the long-wavelength light-emitting layer 15b and the blue light-emitting layer 15c is preferably 1 nm or more and 30 nm or less from the viewpoint of control of the light-emitting region and light-emitting balance, but is not particularly limited.

  As the blue light emitting molecule, a known blue light emitting molecule can be used. The blue light-emitting molecule preferably has a light emission peak around 440 nm to 480 nm. As the green light emitting molecule, a known green light emitting molecule can be used. The green light-emitting molecule preferably has a light emission peak around 515 nm to 550 nm. As the red light emitting molecule, a known red light emitting molecule can be used. The red light-emitting molecule preferably has a light emission peak around 600 nm to 640 nm. Each light emitting molecule may be a fluorescent light emitting material, a phosphorescent light emitting material, or a delayed fluorescent material. As the host material for the long-wavelength light-emitting layer 15b and the blue light-emitting layer 15c, known materials can be used as appropriate. As the host material, a polycyclic compound or a heterocyclic compound such as an anthracene derivative, a pyrene derivative, a carbazole derivative, or an amine derivative can be used. As the host material, a light-emitting material suitable for a light-emitting molecule can be used as appropriate. A host material suitable for emitting blue light-emitting molecules is preferable because it can be used as a host material for the long-wavelength light-emitting layer 15b.

  The light-emitting molecule may have a fluoranthene skeleton, an anthracene skeleton, a pyrene skeleton, or a fluorene skeleton. Among them, it is preferable to have a structure having a fluoranthene skeleton and further forming a ring.

<Light extraction electrode 16>
The light extraction electrode 16 is an electrode on the light extraction side. The light extraction electrode 16 is made of, for example, a metal thin film made of Al, Ag, or an Ag alloy. When a metal thin film is used, an Ag alloy thin film containing an alkaline earth metal such as magnesium (Mg) or calcium (Ca) can be used. Ag alone may be used. The thickness of the light extraction electrode 16 is preferably such that it has a reflectance of 8% or more in the visible light region with respect to the incident light from the organic layer 15 from the viewpoint of enhancing the resonance peak as described later. The thickness is particularly preferably 5 nm or more and 30 nm or less from the viewpoint of transmittance.

<Transparent sealing layer 17>
On the light extraction electrode 16, a transparent sealing layer 17 for preventing permeation of oxygen or moisture from the outside into the organic layer 15 is provided. The transparent sealing layer 17 is made of a material having extremely low permeability to oxygen and moisture from the outside, such as silicon nitride and silicon oxynitride, and serves not only to protect the light emitting element but also to protect the light emitting element from a step of providing a color filter. There is also.

<Interference design>
The organic light emitting device of the present invention has a resonator structure formed between the reflection electrode 13 and the light extraction electrode 16, and has a resonance maximum peak wavelength in a blue wavelength region. White light composed of blue, green, and red emitted from the light emitting layer causes optical interference between the light emitting layer and the reflective electrode 13 and between the reflective electrode 13 and the light extraction electrode 16. At this time, the optical distance between the reflection electrode 13 and the light extraction electrode 16 is set so that the resonance peak is maximized near the blue wavelength region (preferably 430 nm to 490 nm, more preferably 440 nm to 480 nm) in the visible light region. Good to be. Specifically, it is preferable to set an equation for determining the wavelength of the maximum resonance peak as in the following equation (2).
L = (Σφ + 2mπ) × λ ₂ / 4π (2)
L: Wavelength optical distance between the reflective electrode 13 and the light extraction electrode 16 in lambda ₂ Sigma] [phi: the sum of the reflection phase m between the reflective electrode 13 and the light extraction electrode 16 at the wavelength lambda _2: 0 or 1 integer lambda ₂ : wavelength in the blue wavelength region (preferably 430 nm to 490 nm, more preferably 440 nm to 480 nm)

  With such interference conditions, the light emitted from the light emitting layer in the organic layer 15 has an enhanced emission wavelength emitted from the blue light emitting molecule, and the resonance effect of the emission wavelength emitted from the green light emitting molecule and the red light emitting molecule is reduced. , Relative to the resonance effect in the blue emission wavelength region. As a result, the emission intensities of green and red having high visibility are relatively weaker than the blue intensity, so that it is possible to suppress the leakage of green and red light from the blue color filter. This makes it possible to achieve blue chromaticity with high color purity and widen the color gamut. When L is converted into a physical film thickness, the physical film thickness of the organic layer 15 is preferably 70 nm or more and 100 nm or less when m = 0 and 150 nm or more and 220 nm or less when m = 1, from the viewpoint of the refractive index. .

In the organic light emitting device of the present invention, the blue light emitting layer 15c is disposed at a position that satisfies the following expression (1).
z = φ × λ ₁ / 4π (1)
z: the optical distance between the reflective electrode-side interface of the blue light emitting layer 15c and the reflective electrode 13 φ: the reflection phase λ ₁ of the reflective electrode 13 in the emission wavelength region of the blue light emitting layer 15c: the visible light region (preferably 400 nm or more) 700nm or less)

Further, the long wavelength light emitting layer 15b is disposed between the blue light emitting layer 15c and the reflective electrode 13. Preferably, the long-wavelength light-emitting layer 15b is arranged at a position that satisfies the following expression (3).
z ′ = φ ′ × λ ₃ / 4π (3)
z ': Optical distance between the interface on the light extraction electrode side of the long-wavelength light-emitting layer 15b and the reflective electrode 13 φ': Reflection phase λ of the reflective electrode 13 in the light-emitting wavelength region of the green-emitting molecule of the long-wavelength light-emitting layer 15b. _3: green wavelength region less (preferably 560nm or less) by which the wavelength of, lambda ₁ is not less than the emission peak wavelength of the blue light-emitting layer 15c, the emission peak wavelength of the emission molecules green light lambda ₃ is long wavelength light emitting layer 15b When it is less than the above, the interference condition with the light reflected by the reflective electrode 13 having the green and red emission wavelengths emitted from the long wavelength light emitting layer 15b can be further reduced. This is because the long-wavelength light-emitting layer 15b is disposed at a distance that is optically closer to the reflective electrode 13 than the blue light-emitting layer 15c, so that the light emitted from the long-wavelength light-emitting layer 15b reflects green and red light from the reflective electrode 13. This is because the resonance effect due to is weakened. As a result, the emission intensity in the green and red emission wavelength regions can be effectively reduced relative to the emission intensity in the blue emission wavelength. This makes it possible to improve the color purity of each color and obtain a wide color gamut, which is obtained when the emission spectrum emitted from the organic light emitting element passes through the RGB color filter. In order to appropriately enhance the green and red reflection conditions to improve the luminous efficiency, it is preferable that λ ₁ be a wavelength exceeding the luminous peak wavelength of the blue luminescent layer 15c. Further, by adopting such an interference design, the viewing angle dependency can be effectively improved.

Next, the effect of suppressing the viewing angle dependence of the present invention will be described. The following equation (4) is an equation that indicates the strength of the resonance effect of the resonance structure of the organic light emitting device.
G∝cos (φ + 4π × z × cos θ / λ ₄ ) / (A-cos (Σφ-4π × L × cos θ / λ ₄ )) (4)
G: the intensity of resonance effects A: coefficient theta: the radiation angle with respect to the normal direction of the reflective electrode surface phi: reflection phase z of the reflective electrode 13 at the wavelength lambda _4: interface of the reflective electrode 13 side of the blue light-emitting layer 15c at the wavelength lambda ₄ the optical distance between the reflective electrode 13 and the Sigma] [phi: the sum of the reflection phase between the reflective electrode 13 and the light extraction electrode 16 at the wavelength lambda ₄ L: between the reflective electrode 13 and the light extraction electrode 16 at the wavelength lambda ₄ Optical distance

The meaning of this equation is that the numerator on the right side of equation (4) indicates the interference condition of the reflection from the light emitting layer to the reflective electrode 13, and the denominator indicates the interference condition determined by all layers of the organic layer 15. For example, if it is desired to increase G at a certain wavelength λ ₄ , the numerator on the right side of Expression (4) should be maximized and the denominator should be minimized.

Generally, the viewing angle characteristic is deteriorated because light emitted in the oblique direction θ with respect to the normal direction of the reflective electrode surface has a shorter optical distance of interference than light emitted in the perpendicular direction. Is due. Reducing the optical distance means that for light in an oblique direction, the wavelength of the resonance peak designed by the incident light in the front direction shifts to the shorter wavelength side (z × cos θ in Expression (4), As L × cos θ decreases, the wavelength λ ₄ of the interference condition shortens accordingly.) On the other hand, the interference increases at the red wavelength as θ increases. This is because the condition is such that resonance occurs in the red wavelength region at a low interference order. For example, in the vicinity of λ ₂ = 800 nm, L = approximately L = 315 nm at m = 0 in equation (2), and the optical distance is equivalent to L = 365 nm at λ ₂ = 440 nm in m = 1 in equation (2). It has become.

  This will be described more specifically with reference to the simulation results shown in FIG. FIG. 2 is a diagram illustrating a relationship between the front (vertical) and the wavelength in an oblique direction of the resonance effect intensity. FIG. 2A is a simulation result of an element in which the blue light emitting layer 15c is disposed between the long wavelength light emitting layer 15b and the reflective electrode 13, and FIG. 2B is a simulation result of the element of the present invention. .

  In FIG. 2A, when the optical distance L is shortened by oblique incidence at 30 °, it becomes easier to match the red interference condition in the low-order interference condition, and the interference intensity changes from green to the vicinity of the red region (see FIG. 2A). “A”) in the parentheses) increases. For this reason, the spectrum change radiated in the green to red region in the oblique direction with respect to the EL spectrum in the front direction becomes large, so that the emission intensity balance of blue, green, and red is broken, and the viewing angle characteristic is deteriorated.

  On the other hand, in the present invention, Expression (1) regarding the arrangement of the blue light emitting layer 15c is satisfied, and the long wavelength light emitting layer 15b is disposed between the blue light emitting layer 15c and the reflective electrode 13. This makes it possible to remove the condition that green and red light emitted from the long-wavelength light-emitting layer 15b in the front direction strengthen the reflection of the reflective electrode 13 (the numerator of the formula (4) can be reduced). In this case, the interference condition for reflection is further deviated in the oblique direction (the numerator of the formula (4) is further reduced). Therefore, as shown in FIG. 2B, the change “b” in the interference intensity in the long wavelength region is smaller than that in “a” in FIG. 2A, and the intensity of the resonance effect with respect to oblique radiation is reduced. It works to suppress the change from green to red. Since it is possible to suppress the change in the green and red light emission intensity in the oblique direction, it is possible to suppress the color shift due to the change in the resonance effect in the green to red region, and it is possible to expect an improvement in the viewing angle characteristics.

  Further, in the present invention, both the green and red molecules emit light in the long-wavelength light emitting layer 15b, so that even if a change in the charge injection balance or a change in the charge recombination balance occurs, the green and red light emission positions are not changed. Change no longer happens individually. Therefore, the interference design becomes easier, and a change in the light emission balance with respect to the change can be suppressed, which leads to an improvement in yield.

  In the interference design as described above, it is possible to determine whether or not the interference position is appropriate by irradiating the manufactured element with incident light substantially perpendicularly and observing the absorption peak of the spectrum of the reflected light. The maximum position of the resonance can be known by paying attention to the surface reflection and the medium on the incident side. The physical film thickness can also be measured by examining the organic film thickness from an image such as a cross-sectional SEM.

≫Apparatus using organic light emitting element 素 子
In the organic light emitting element according to the present embodiment, the light emission luminance is controlled by a TFT which is an example of a switching element, and an image can be displayed with each light emission luminance by providing the organic light emitting element in a plurality of planes. The switching element according to the present embodiment is not limited to a TFT, and may be a transistor, an MIM element, or an active matrix driver formed on a substrate such as a Si substrate. On the substrate can also be referred to as within the substrate. This is selected depending on the definition. For example, in the case of a definition of about 1 inch and QVGA, it is preferable to provide an organic light emitting element on a Si substrate. By driving the display device using the organic light emitting device according to the present embodiment, stable display can be performed with good image quality and long-time display.

<Display device>
FIG. 3 is a schematic cross-sectional view showing an example of a full-color top emission type display device using the organic light emitting device according to the present embodiment. This display device includes a large number of organic light emitting elements 100 (100R, 100G, 100B) arranged in a matrix on a substrate 10. Many organic light emitting devices 100 are separated by banks 14. In the present embodiment, the substrate 10 may be transparent or opaque because of the top emission method. Wiring for supplying power and emitting light is arranged on the reflection electrodes 13 (13R, 13G, 13B) and the light extraction electrodes 16 which are pixel electrodes (not shown). In the organic light emitting element 100, color filters 18 (18R, 18G, 18B) that selectively transmit red (R), green (G), and blue (B) are arranged corresponding to the respective color pixels, and each emits red light. An element (100R), a green light emitting element (100G), and a blue light emitting element (100B). In the color filter 18, the red, green, and blue colors may be arranged in a delta arrangement. A transparent protective substrate 20 such as glass or plastic may be disposed on the color filter 18 to protect the outermost surface.

  FIG. 4 is a schematic diagram illustrating an example of the display device according to the present embodiment. The display device 1000 may include a touch panel 1003, a display panel 1005, a frame 1006, a circuit board 1007, and a battery 1008 between the upper cover 1001 and the lower cover 1009. The touch panel 1003 and the display panel 1005 are connected to flexible printed circuits FPCs 1002 and 1004. The organic light-emitting device according to this embodiment may be used for the display panel 1005. Transistors are printed on the circuit board 1007. The battery 1008 need not be provided if the display device is not a portable device, and need not be provided at this position even if the display device is a portable device.

  FIG. 5 is a schematic diagram illustrating an example of the display device according to the present embodiment. FIG. 5A shows a display device such as a television monitor or a PC monitor. The display device 1300 has a frame 1301 and a display portion 1302. The organic light emitting element according to the embodiment may be used for the display unit 1302. In addition, the display device 1300 includes a frame 1301 and a base 1303 that supports the display unit 1302. The base 1303 is not limited to the form shown in FIG. The lower side of the frame 1301 may also serve as a base. Further, the frame 1301 and the display unit 1302 may be curved. The radius of curvature may be 5000 mm or more and 6000 mm or less. The display device 1310 in FIG. 5B is configured to be bendable, and is a so-called folderable display device. The display device 1310 includes a first display portion 1311, a second display portion 1312, a housing 1313, and a bending point 1314. The first display unit 1311 and the second display unit 1312 may include the organic light emitting device according to the embodiment. The first display unit 1311 and the second display unit 1312 may be one seamless display device. The first display unit 1311 and the second display unit 1312 can be separated by a bending point. The first display unit 1311 and the second display unit 1312 may display different images, respectively, or may display one image with the first and second display units.

<Imaging device>
The display device according to the present embodiment may be used for a display unit of an imaging device that includes an optical unit having a plurality of lenses and an image sensor that receives light passing through the optical unit. The imaging device may include a display unit that displays information acquired by the imaging device. Further, the display unit may be a display unit exposed to the outside of the imaging device or a display unit arranged in a viewfinder. The imaging device may be a digital camera or a digital video camera.

  FIG. 6 is a schematic diagram illustrating an example of the imaging device according to the present embodiment. The imaging device 1100 may include a viewfinder 1101, a rear display 1102, a housing 1103, and an operation unit 1104. The viewfinder 1101 may include the display device according to the present embodiment. In that case, the display device may display not only the image to be captured but also environment information, an imaging instruction, and the like. The environmental information may include the intensity of the external light, the direction of the external light, the moving speed of the subject, the possibility that the subject is blocked by a blocking object, and the like. Since the timing suitable for imaging is a short time, it is better to display information as soon as possible. Therefore, it is preferable to use a display device using the organic light emitting device of the present invention. This is because the organic light emitting device has a high response speed. A display device using an organic light emitting element can be more suitably used in a device requiring a display speed than a liquid crystal display device. The imaging device 1100 has an optical unit (not shown). The optical unit has a plurality of lenses, and forms an image on an imaging element housed in the housing 1103. The focus of the plurality of lenses can be adjusted by adjusting their relative positions. This operation can be performed automatically.

<Portable devices>
The display device according to the present embodiment may be used for a display unit of a portable device such as a portable terminal. In that case, both the display function and the operation function may be provided. Examples of the mobile terminal include a mobile phone such as a smartphone, a tablet, and a head-mounted display.

  FIG. 7 is a schematic diagram illustrating an example of the mobile device according to the present embodiment. The mobile device 1200 includes a display unit 1201, an operation unit 1202, and a housing 1203. The housing 1203 may include a circuit, a printed circuit board including the circuit, a battery, and a communication unit. The operation unit 1202 may be a button or a touch panel type reaction unit. The operation unit may be a biometric recognition unit that recognizes a fingerprint and unlocks the lock. A portable device having a communication unit can also be called a communication device.

<Lighting device>
FIG. 8 is a schematic diagram illustrating an example of a lighting device according to the present embodiment. The lighting device 1400 may include a housing 1401, a light source 1402, a circuit board 1403, an optical filter 1404, and a light diffusion unit 1405. The light source 1402 may include the organic light emitting device according to the embodiment. The optical filter 1404 may be a filter that improves the color rendering of the light source 1402. The light diffusing unit 1405 can effectively diffuse the light of the light source 1402 such as light-up and deliver the light to a wide range. If necessary, a cover may be provided on the outermost side.

  The lighting device is, for example, a device that illuminates a room. The lighting device may emit white, neutral white, or any other color from blue to red. It may have a dimming circuit for dimming them. The lighting device may include the organic light emitting device of the present invention and a power supply circuit connected thereto. The power supply circuit is a circuit that converts an AC voltage into a DC voltage. White has a color temperature of 4200K and neutral white has a color temperature of 5000K. The lighting device may have a color filter.

<Example 1>
The optical characteristics of the organic light emitting device shown in FIG. 1A were evaluated by simulation.

  The simulation conditions will be described. The reflection electrode 13 was made of aluminum of 60 nm, and was used as a high reflectance reflection layer. The film thickness of each of the long wavelength light emitting layer 15b and the blue light emitting layer 15c was 10 nm. The film thicknesses of the hole transport layer 15a and the electron transport layer 15d were as shown below. That is, under the condition that the value of the blueness CIE_y in CIE1931 in the spectrum after passing through the RGB color filter is 0.06, the RGB intensity ratio for obtaining white light emission from each RGB emission spectrum is estimated, and the power consumption is the least. The thickness was set to such a value. The light extraction electrode 16 was made of an MgAg alloy and had a thickness of 10 nm. The transparent sealing layer 17 was a SiN film. The simulation investigated the EL spectrum emitted to the transparent sealing layer 17.

In the simulation, it was assumed that each luminescent molecule emitted the same number of luminescent photons in the luminescent layer. The fluorescence spectrum and the resonance effect formed between the reflection electrode 13 and the light extraction electrode 16 were estimated, and the EL spectrum was simulated by multiplying them. FIG. 9A shows the fluorescence spectrum of the luminescent molecule used. Further, an EL spectrum for each color pixel is obtained by multiplying the obtained EL spectrum by the spectral characteristics of each color of the color filter 18 shown in FIG. At this time, the power consumption is minimized under the condition that the blueness CIE_y is 0.06. Table 1 shows details of the conditions for the organic layer 15. With respect to z, L, λ ₁ , and λ ₂ , the refractive index of the organic layer material was 2.05, φ = 0.77π in equation (1), Δφ = 1.37π in equation (2), and m = 1. did. λ ₃ was calculated assuming that the refractive index of the organic layer material was 1.90 and φ ′ = 0.82π in equation (3).

  The power consumption and the color reproduction range were evaluated from the EL spectrum for each color pixel. Regarding power consumption, a luminance ratio when white (0.31, 0.33) having a certain luminance is output is converted from chromaticity of red, green, and blue obtained for each color, and a constant voltage is obtained. Power consumption was estimated. The relative power consumption with the power consumption of Comparative Example 1 as 1 was estimated.

  Regarding the viewing angle dependency, a case where the light was radiated into the transparent sealing layer 17 at 30 ° with respect to the normal direction of the substrate was simulated. The color reproduction range in the front direction and the white color shift when oblique were evaluated, and the viewing angle dependency was evaluated from the change in the color reproduction range. Regarding the white color shift when oblique, the amount of input current in each pixel is set based on the intensity ratio of each pixel for emitting white in the front direction, and the white current obtained from the radiant intensity of each pixel in the oblique direction based on the current amount ratio The difference between the light and the white chromaticity in the front direction was evaluated by Δu′v ′.

  The light emitting positions of the long-wavelength light emitting layer 15b and the blue light emitting layer 15c are those where the light extraction electrode 16 side is the light emitting position, the center portion is the light emitting position, and the reflective electrode 13 side is the light emitting position. Table 2 shows the average value of each characteristic under each condition.

<Example 2, Comparative Examples 1, 2, 3>
Evaluation was performed in the same manner as in Example 1 except that the layer configuration and the film thickness of the organic layer 15 were changed as shown in Table 1. Note that z ′ and λ ₃ in Comparative Example 3 were determined by regarding the green light emitting layer as a long wavelength light emitting layer. Table 2 shows the evaluation results.

<Examples 3, 4 and Comparative Examples 4, 5, 6>
Relative power consumption using the light-emitting molecules having the fluorescence spectrum shown in FIG. 9B and changing the layer configuration and film thickness of the organic layer 15 as shown in Table 1 and setting the power consumption to 1 in Comparative Example 6 The evaluation was performed in the same manner as in Example 1, except for the estimation. Note that z ′ and λ ₃ in Comparative Example 6 were determined by regarding the green light emitting layer as a long wavelength light emitting layer. Table 3 shows the evaluation results.

  From the results of Tables 2 and 3, it was confirmed that the NTSC value in the front direction was increased and Δu′v ′ was suppressed in the example of the present invention as compared with the comparative example, and that the white organic light emitting device of the present invention had a wider color gamut and a wider field of view. The effect of improving the angular characteristics was confirmed.

  Further, the same effect was confirmed even when the reflection electrode 13 was simulated with Al (60 nm) / Ti (10 nm) in which Ti was laminated as a barrier layer on an Al thin film.

10: substrate, 13: reflective electrode, 14: bank, 15: organic layer, 15b: long wavelength light emitting layer, 15c: blue light emitting layer, 16: light extraction electrode, 17: transparent sealing layer, 18: color filter, 20 ： Protective substrate

Claims (12)

A reflective organic electrode, an organic layer, and a light extraction electrode, a white organic light-emitting element having, in this order,
The organic layer has a blue light emitting layer containing a light emitting molecule that emits blue light, and a long wavelength light emitting layer containing a light emitting molecule that emits red light and a light emitting molecule that emits green light,
The long-wavelength light-emitting layer is disposed between the blue light-emitting layer and the reflective electrode,
The blue light emitting layer is disposed at a position satisfying the following formula (1):
A white organic light emitting device having a resonator structure formed between the reflection electrode and the light extraction electrode, and having a resonance maximum peak wavelength in a blue wavelength region.
z = φ × λ ₁ / 4π (1)
z: the optical distance between the interface of the blue light emitting layer on the reflective electrode side and the reflective electrode φ: the reflection phase λ _{1 of the} reflective electrode in the emission wavelength region of the blue light emitting layer: wavelength in the visible light region The white organic light emitting device according to claim 1, wherein the following formula (2) is satisfied.
L = (Σφ + 2mπ) × λ ₂ / 4π (2)
L: optical distance between the reflective electrode and the light extraction electrode at the wavelength lambda ₂ Sigma] [phi: the sum of the reflection phase between the light extraction electrode and the reflective electrode at the wavelength lambda ₂ m: 0 or 1 integer lambda ₂ : wavelength within the blue wavelength range   The white organic light emitting device according to claim 1, wherein the blue wavelength region is a region including a light emission peak wavelength of the blue light emitting layer.   The white organic light emitting device according to any one of claims 1 to 3, wherein the blue wavelength region is a region from 430 nm to 490 nm.   The white organic light-emitting device according to any one of claims 1 to 4, wherein the physical thickness of the organic layer is 150 nm or more and 220 nm or less. The wavelength λ ₁ is equal to or longer than the emission peak wavelength of the blue light emitting layer, and the wavelength λ ₃ in the following formula (3) is shorter than the emission peak wavelength of the green light emitting molecule. 6. The white organic light-emitting device according to any one of 5.
z ′ = φ ′ × λ ₃ / 4π (3)
z ′: optical distance between the interface of the long wavelength light emitting layer on the light extraction electrode side and the reflective electrode φ ′: reflection phase of the reflective electrode in the emission wavelength region of the green light-emitting molecule The white organic light emitting device according to claim 1, wherein the λ ₁ is a wavelength exceeding a light emission peak wavelength of the blue light emitting layer.   The white organic light emitting device according to any one of claims 1 to 7, wherein the light extraction electrode is made of an Ag alloy.   A display device, comprising: the white organic light-emitting device according to claim 1; and a color filter.   An imaging device, comprising: an imaging element; and a display unit that displays information obtained by the imaging element, wherein the display unit is the display device according to claim 9.   A mobile device having a display unit, wherein the display unit is the display device according to claim 9.   A lighting device comprising: the white organic light-emitting element according to claim 1; and a power supply circuit connected to the white organic light-emitting element.

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